1. Field of the Invention
The present invention relates to a protection circuit to be inserted into an analog signals transmission line, circuit furnished with a supply terminal, an earth terminal, an input terminal and an output terminal, circuit comprising a first so-called series transistor, a current-receiving electrode of which is linked to a terminal to which is applied a voltage substantially equal to the voltage of the input terminal whilst a current-delivery electrode of this transistor feeds an output terminal, and a second transistor for controlling the first.
2. Description of the Related Art
A protection circuit is known from the document DE-OS-28 12 157. According to this document, a switching transistor inserted into a line is associated with an auxiliary transistor switched on by a signal at the terminals of a resistor for measuring the current, which adds current into the base of the switching transistor.
An object of the invention is to make the circuit still more efficient.
For this purpose, the second transistor is mounted as an amplifier, with a current-receiving electrode loaded by a so-called top load element linked to the supply terminal, a current-delivery electrode loaded by a so-called bottom load element linked to earth, and a control electrode wired up in such a way that the voltage of the input terminal is substantially applied thereto, whilst a control electrode of the series transistor is linked to the second transistor on the top load element side.
Particular modes of implementation of the invention appear in the dependent claims 2 to 6.